Fig. 5.

Loss of Msmo1 and Lss activities disrupts growth plate patterning. (A-P) Expression domains of col2a1a (A,D,G,J), col10a1a (B,E,H,K,M-P) and msmo1 (C,F,I,L) were analyzed within growth plates of wild type (A-C), kol^nu7 (D-F), Tg(fabp10a:msmo1:pA)^nu100;msmo1^nu81 (G-I) and Tg(fabp10:lss:pA)^nu101;lss^nu60 (J-L) using RNAscope in situ hybridization. (A) Strong col2a1a expression is observed in round and stacked chondrocytes in wild type, corresponding to presumed resting and proliferating chondrocytes. (B) Expression of col10a1a in wild type is observed complementary to col2a1a expression in presumed hypertrophic chondrocytes. The expression of col2a1a is expanded in kol^nu7 (D) and Tg(fabp10a:msmo1:pA)^nu100;msmo1^nu81 (G) growth plates, with a near-complete loss of col10a1a expression in kol^nu7 (E) and Tg(fabp10a:msmo1:pA)^nu100;msmo1^nu81 (H). Expression of col2a1a (J) and col10a1a (K) in Tg(fabp10:lss:pA)^nu101;lss^nu60 appears less affected when compared to kol^nu7(D,E) and Tg(fabp10a:msmo1:pA)^nu100;msmo1^nu81 (G,H). Expression of msmo1 is detected primarily in pre-hypertrophic chondrocytes of wild type (C); msmo1 expression is undetectable in kol^nu7 growth plates (F), but is upregulated in transgenically rescued msmo1^nu81 (I) and lss^nu60 (L) mutants. (M-P) Expression of col10a1a in osteoblasts is unchanged between wild type and mutants. Images represent paraffin sections of the pterotic at 2 months of age (∼15 mm SL). Boxed areas in A-L are shown at higher magnification in A′-L′. Scale bars: 100 μm. Tg*, Tg(fabp10:msmo1:pA)^nu100; Tg**, Tg(fabp10:lss:pA)^nu101. wt n=6, kol^nu7 n=6, Tg(fabp10a:msmo1:pA)^nu100;msmo1^nu81 n=3, Tg(fabp10:lss:pA)^nu101;lss^nu60 n=3.